Liam Fox has been accused of being vague and confused about the country's post-Brexit trading status after saying Britain would leave "no legal vacuum" with the world after leaving the European Union.

The International Trade Secretary told the World Trade Organisation (WTO) that the UK would continue to uphold its international trading commitments after Brexit.

But critics said he was sending out mixed messages following weekend reports that he would use his speech to signal support for pulling the UK out of the EU customs union so he could legally strike new trade deals around the world.

Instead, Dr Fox told the WTO in Geneva: "The UK is a full and founding member of the WTO.

"We have our own schedules that we currently share with the rest of the EU. These set out our national commitments in the international trading system.

"The UK will continue to uphold these commitments when we leave the European Union.

"There will be no legal vacuum but this will not stop us pursuing a more liberalised trade agenda in the future."

Labour former business minister Pat McFadden said Dr Fox has a duty to set out the details on whether the UK will pull out of the customs union, or remain a member of the European single market.

He also warned against "sleepwalking" into a trading system that relies on WTO rules because key sectors such as the car industry would face "high and destructive" tariffs.

Commenting for the Open Britain campaign, Mr McFadden said: "From a Government promising an ambitious global trade agenda, Liam Fox's speech was pathetically vague and bromide-filled.

"Dr Fox needs to spell out the details - whether Britain will leave the customs union, whether we will continue to be a member of the single market, and what will happen to the trade deals the EU has signed on our behalf with more than 50 countries.

"The public have a right to know before the Government makes crucial decisions on our trading future."

Vote Leave Watch chairman Chuka Umunna said Dr Fox's failure to mention the customs union or make a major announcement in his speech showed the Government was "totally confused" about single market membership.

The Labour MP said: "For Liam Fox to brief the Sunday papers that he would give a major announcement, before delivering bland platitudes today, showcases the total confusion at the heart of Government on this issue.

"Vote Leavers promised that Britain would rapidly sign global free trade deals, while keeping full access to the single market. We are yet to see any detail as to how that might be achieved."

Liberal Democrat leader Tim Farron said: "At a time when the business community needs clarity and stability, Liam Fox is saying one thing to the papers and another to our international allies.

"Not content with insulting British businesses, it seems he now wants to confuse them by sending mixed messages about our membership of the single market.

"Clearly, Liam Fox is incapable of speaking for our Government or country; he is a second-class Cabinet minister enjoying first-class travel around the world."

But Economists for Brexit said Dr Fox had signalled the first steps towards a future outside the single market, with Britain having its own free trade agreements around the globe.

Its co-chair Patrick Minford said such an arrangement could boost GDP by 4%.

"We now appear to see (the) Government signalling the first steps in the right direction, but many still fail to appreciate rather than just being the default position in the absence of a trade deal with the EU in order to deliver the type of Brexit the UK electorate voted for, leaving the single market is in fact the optimal option for the UK economy," he said.

Meanwhile, Iain Duncan Smith dismissed George Osborne's warnings against a "hard Brexit" with the UK leaving the single market, in the latest sign of Tory splits over how to quit the EU.

Ahead of the party's annual conference, Mr Duncan Smith rejected the former chancellor's argument that Britain must compromise with the EU in order to get a Brexit deal acceptable to the "liberal mainstream majority".

The ex-Tory leader instead insisted that "the British people voted to take back control of their borders, their money and their laws; that seems pretty mainstream to me".